Wireless device with filters to support co-existence in adjacent frequency bands

Abstract

Techniques for using a narrow filter located before a power amplifier to reduce interference in an adjacent frequency band are disclosed. In an exemplary design, an apparatus (e.g., a wireless device) includes the narrow filter and the power amplifier. The narrow filter is for a first frequency band (e.g., Band 40) and has a first bandwidth that is more narrow than the first frequency band. The narrow filter receives and filters an input radio frequency (RF) signal and provides a filtered RF signal. The power amplifier receives and amplifies the filtered RF signal and provides an amplified RF signal. The apparatus may further include a full filter for the first frequency band and located after the power amplifier. The full filter receives and filters the amplified RF signal and provides an output RF signal when it is selected for use.

What is claimed is: 
     
       1. An apparatus comprising:
 a narrow filter for a first frequency band and having a first bandwidth more narrow than the first frequency band, the narrow filter being configured as a passband filter to receive and filter an input radio frequency (RF) signal and provide a filtered RF signal; 
 a power amplifier having an input operatively coupled to an output of the narrow filter, the power amplifier being configured to receive and amplify the filtered RF signal and provide an amplified RF signal; 
 a first signal path comprising the narrow filter and coupled to a second signal path via a first switch; and 
 a bypass signal path coupled to the second signal path via a second switch, 
 wherein the second signal path is coupled to an input of the power amplifier. 
 
     
     
       2. The apparatus of  claim 1 , further comprising:
 a full filter for the first frequency band and having a second bandwidth larger than the first bandwidth of the narrow filter, the full filter having an input operatively coupled to an output of the power amplifier, the full filter being configured to receive and filter the amplified RF signal and provide an output RF signal. 
 
     
     
       3. The apparatus of  claim 2 , the first frequency band corresponding to Band  40 , the first bandwidth of the narrow filter being within Band  40  and smaller than a bandwidth of Band  40 , and the second bandwidth of the full filter being equal to or larger than the bandwidth of Band  40 , wherein Band  40  is from 2300 to 2400 MHz. 
     
     
       4. The apparatus of  claim 2 , the narrow filter having a transition band within the first frequency band, and the full filter having transition bands outside the first frequency band. 
     
     
       5. The apparatus of  claim 1 , further comprising:
 a second narrow filter for the first frequency band and having a bandwidth more narrow than the first frequency band, the second narrow filter having an input operatively coupled to an output of the power amplifier, the second narrow filter being configured to receive and filter the amplified RF signal and provide an output RF signal. 
 
     
     
       6. The apparatus of  claim 1 , further comprising:
 a bypass signal path coupled between the output of the power amplifier and an antenna interface circuit. 
 
     
     
       7. The apparatus of  claim 1 , the narrow filter being selected or bypassed based on at least one criteria, and the narrow filter being configured to filter the input RF signal for the first frequency band when the narrow filter is selected. 
     
     
       8. The apparatus of  claim 1 , the narrow filter being selected when the apparatus concurrently communicates with a first wireless network in the first frequency band and with a second wireless network in a second frequency band adjacent to the first frequency band. 
     
     
       9. The apparatus of  claim 2 , the full filter being selected when the apparatus communicates with a first wireless network in the first frequency band but not with a second wireless network in a second frequency band adjacent to the first frequency band. 
     
     
       10. The apparatus of  claim 2 , the narrow filter and the full filter being both selected when the apparatus concurrently communicates with a first wireless network in the first frequency band and with a second wireless network in a second frequency band adjacent to the first frequency band. 
     
     
       11. The apparatus of  claim 5 , the narrow filter and the second narrow filter being both selected when the apparatus concurrently communicates with a first wireless network in the first frequency band and with a second wireless network in a second frequency band adjacent to the first frequency band. 
     
     
       12. A method comprising:
 filtering an input radio frequency (RF) signal with a narrow filter configured as a passband filter to obtain a filtered RF signal, the narrow filter being for a first frequency band and having a first bandwidth more narrow than the first frequency band; and 
 amplifying the filtered RF signal from the narrow filter with a power amplifier to obtain an amplified RF signal, 
 wherein the narrow filter is selected when concurrently communicating with a first wireless network in the first frequency band and with a second wireless network in a second frequency band adjacent to the first frequency band. 
 
     
     
       13. The method of  claim 12 , further comprising:
 filtering the amplified RF signal from the power amplifier with a full filter to obtain an output RF signal, the full filter being for the first frequency band and having a second bandwidth larger than the first bandwidth of the narrow filter. 
 
     
     
       14. The method of  claim 12 , further comprising:
 filtering the amplified RF signal from the power amplifier with a second narrow filter to obtain an output RF signal, the second narrow filter being for the first frequency band and having a bandwidth more narrow than the first frequency band. 
 
     
     
       15. The method of  claim 12 , further comprising:
 amplifying the input RF signal with the power amplifier and bypassing the narrow filter when the narrow filter is not selected for use. 
 
     
     
       16. An apparatus comprising:
 first means for filtering configured as a passband filter to receive and filter an input radio frequency (RF) signal and provide a filtered RF signal, the first means for filtering being for a first frequency band and having a first bandwidth more narrow than the first frequency band; 
 means for amplifying configured to receive and amplify the filtered RF signal and provide an amplified RF signal; 
 a first signal path comprising the first means for filtering, the first signal path being coupled to a second signal path via a first means for switching; and 
 a bypass signal path coupled to the second signal path via a second means for switching, 
 wherein the second signal path is coupled to an input of the means for amplifying. 
 
     
     
       17. The apparatus of  claim 16 , further comprising:
 second means for filtering configured to receive and filter the amplified RF signal and provide an output RF signal, the second means for filtering being for the first frequency band and having a second bandwidth larger than the first bandwidth of the narrow filter. 
 
     
     
       18. The apparatus of  claim 16 , further comprising:
 second means for filtering configured to receive and filter the amplified RF signal and provide an output RF signal, the second means for filtering being for the first frequency band and having a bandwidth more narrow than the first frequency band. 
 
     
     
       19. A computer program product, comprising:
 a non-transitory computer-readable medium comprising: 
 code for causing at least one computer to select a narrow filter configured as a passband filter to filter an input radio frequency (RF) signal and provide a filtered RF signal when a wireless device concurrently communicates with a first wireless network in a first frequency band and with a second wireless network in a second frequency band adjacent to the first frequency band, the narrow filter being for the first frequency band and having a first bandwidth more narrow than the first frequency band, the narrow filter being located prior to a power amplifier; and 
 code for causing the at least one computer to select a full filter to filter an amplified RF signal from the power amplifier and provide an output RF signal when the wireless device communicates with the first wireless network in the first frequency band but not with the second wireless network in the second frequency band, the full filter being for the first frequency band and having a second bandwidth larger than the first bandwidth of the narrow filter, the full filter being located after the power amplifier. 
 
     
     
       20. The apparatus of  claim 1 , wherein the first switch is coupled to an input of the narrow filter, and wherein the first signal path is coupled to the second signal path via the first switch and a second switch coupled to an output of the narrow filter. 
     
     
       21. The apparatus of  claim 1 , further comprising a third signal path over which the input RF signal is received, wherein the apparatus is configured to selectively couple the first signal path to the third signal path and to selectively couple the bypass signal path to the third signal path.